1. Field of Invention
This invention relates to heat absorbing devices, specifically to such devices which are used for extracting the heat radiation from the pinch area of several incandescent lamp bases.
2. Description of Prior Art
Improved incandescent lamps using tungsten filaments with a halogen type gas, both encapsulated in a quartz glass envelope have been around for many years. Halogen lamps give off considerable amounts of infrared radiation or heat energy. It is estimated that only 13% of the electrical energy going through a lamp filament will go towards actual light output. The remaining 87% is converted directly to heat energy.
Halogen lamps with short light center lengths (LCL) and greater lamp output power in excess of 400 watts or so, apply more heat stress to the lamp seal region. This so-called squeeze point or neck, is the physical area of constriction of the lamp located at the base of the lamp. Another term for this region is the pinch area. The pinch in a lamp is one of the most critical areas. It is the area of the quartz glass envelope that is sealed between the exterior of the envelope and the gas filled interior that houses the filament of the lamp. In this pinch area, two conductors carry the current in and out of the filament of the lamp. The electrical current subjects the pinch area to high temperatures. At high operating temperatures, oxidation of the filament lead-in and lead-out conductors, or slight mismatches between the coefficient of expansion of the quartz glass and these conductors will cause the pinch area to crack, and therefore compromise the effectiveness of the air-tight pinch. If the halogen lamp is overheated, the oxidation of the pinch will lead to premature lamp failure. For example, a halogen with an expected lamp life of 250 hours will have a maximum pinch area operating temperature of 400 degrees Celsius. Exceed the pinch area temperature of 400 degrees Celsius and the lamp will fail sooner. Obviously, a lamp will not burn forever. Ordinarily, the material in the filament evaporates in time, and will cause the filament to weaken and collapse. The filament may short together to create a hot spot. The hot spot in turn draws more current and will cause the filament to explode and break apart all together.
If overheating of the lamp can be avoided and the pinch area temperature is kept at the critical level of about 350 degrees Celsius or lower during normal use, the halogen lamp can be expected to last longer. There have been many attempts to devise a method to keep the pinch area temperature of a lamp below the critical level. Heat shields have been used in systems comprising of a lamp source, lamp socket, and reflector. The disadvantage here is that the heat shield was used to deflect the heat generated by the lamp source away from the reflector, lamp socket, or lamp housing, but did little or nothing to keep the lamp source cool. Other prior art have shown inventions suggesting or using heat sinks with fins attached to the rear surface of a reflector in a lamp housing. Again, the inventions cooled the reflector, but the lamp did not benefit directly from these designs. Yet, some inventions called for the cooling of the lamp source by attaching heat dissipating fins to the mount supporting the socket that holds the lamp, or to the socket itself. This again did not directly benefit the lamp and its critical pinch area, but cooled the socket more so. Lastly, present lamp sources with integral heat sinking and cooling fins manufactured as part of the lamp, do not provide convenient and modular use with a variety of other types of lamps with varying filament designs and layouts. The disadvantage here is that the lamps manufactured with integral heat sinks can only be used in light fixtures designed to accommodate such lamps, thereby limiting their usage.